1. Field of the Invention
The present invention relates to an image converting method and related image converting module, and more particularly, to an image converting method capable of converting a low dynamic range image to a high dynamic range image and related image converting module.
2. Description of the Prior Art
The dynamic range of a scene is defined to be a ratio of the highest scene luminance to the lowest scene luminance. Generally speaking, a conventional display device such as a liquid crystal display (LCD) or a television has a dynamic range of about 250:1, and covers about half of the visible color gamut. However, the human vision system (HVS) has a dynamic range greater than 10,000:1, and is capable of distinguishing about 10,000 colors at a given brightness.
Typically, the image displayed on the conventional display device corresponds to intensities spanning 256 gray levels. That is, each color channel (red, green, and blue) is determined by 8 bits. Therefore, the minimum gray level is equal to 0, and the maximum gray level is equal to 255. From the above description, it is obvious that the dynamic range in the real-world environment far exceeds the representable dynamic range shown on the conventional display device.
In recent years, a high-end display device may feature high dynamic range (HDR), to expand its contrast ratio and to display more realistic, natural images. Although the high-end display device is able to display the HDR images, most of image contents are still stored by the conventional format (e.g. low dynamic range (LDR) images). Thus, how to convert the LDR images to the HDR images capable of being displayed by the display device of HDR becomes a topic to be discussed.